Member for plasma etching device and method for manufacture thereof

ABSTRACT

A member for a plasma etching device, comprising a coating film of yttrium oxide or YAG having a coating film thickness of 10 μm or more, a coating film thickness variance of 15% or less, preferably a surface roughness (Ra) of 1 μm or less, formed on a surface of a member, comprising quartz glass which contains 1 to 10% by weight of yttrium oxide or YAG. The member for a plasma etching device has high plasma resistance, is not subjected to an abnormal etching on the basis of a partial change of electric properties and, accordingly, can be used for a long period of time. Even when the member is large enough to handle 12-inch Si wafers, the above-described advantageous properties are maintained and the member can be used for a long period of time.

TECHNICAL FIELD

The present invention relates to a member for use in a plasma etchingapparatus for a semiconductor device and, particularly, to a member fora plasma etching apparatus coated with a coating film of yttrium oxideor YAG.

BACKGROUND ART

Heretofore, in a production process of a semiconductor device, anetching treatment has been performed on a thin film on an Si wafer bymaking use of an ion or a radical generated in a plasma. As for suchplasma etching treatment method, there is, for example, a method inwhich a thin film on a surface of an Si wafer is etched by a chemicaletching mechanism or a physical etching mechanism, or a method in whichthe thin film is anisotropically etched by electrically accelerating aspeed of an ion and, then, drawing it to the surface of the Si wafer. Atthe time of performing the plasma etching treatment, a member or acontainer (hereinafter referred to also as “member”) containing quartzglass, aluminum, alumite or the like has ordinarily been used. On thisoccasion, there is a problem in that a surface of the member itself isalso etched and, then, a particle is generated, to thereby contaminate asemiconductor device. For this account, a method in which a tapecontaining a fluorocarbon resin or an engineering plastic is applied ona surface of the member for the sake of convenience or a method in whicha coating film containing the above-described resin is formed has beenproposed. However, in the method for applying the tape, since a filmthickness of the tape itself is small, etching resistance is notsufficient and also, since a joint portion is formed by applying thetape, a plasma ion is penetrated into a gap formed on this portion and,then, a substrate is partially etched or, since it is difficult touniformly apply the tape on the surface, a gap is partially generatedbetween the substrate and the tape and, due to the gap, an irregularityis generated on the surface and, then, an irregularity of electricproperties is generated on the surface and, due to this irregularity, aninsulation failure is partially generated, to thereby cause such aproblem as generating a pinhole in the tape. Further, there is adrawback in that a contaminant is released from an adhesive of the tapeand, then, properties of the Si wafer are deteriorated.

Further, as for the member which has been coated with the conventionalfluorocarbon resin or engineering plastic, since a surface thereof tendsto be roughened, the plasma is not well generated and there is also adrawback in that a pinhole is generated in the film or the like.

In order to solve these drawbacks of members containing quartz glass,aluminum, alumina or the like, a member containing ceramics which areexcellent in plasma resistance is proposed in JP-A-2001-118910 or thelike. However, there is a problem in that a crack or a bent is generatedin the member containing the above-described ceramics at the time ofcalcining and, then, preparation of a large-sized member is not onlydifficult but also expensive.

Thus, a first object of the present invention is to provide a member fora plasma etching apparatus which has a high plasma resistance, does notperform any abnormal etching to be caused by a partial change ofelectrical properties and can be used for a long period of time.

Further, a second object of the present invention is to provide a memberfor a plasma etching apparatus which can handle such a large-sizedsemiconductor device as being a 12-inch Si wafer.

Still further, a third object of the present invention is to provide amethod for producing the above-described member for the plasma etchingapparatus.

DISCLOSURE OF THE INVENTION

The present invention relates to a member for a plasma etching apparatusin which a coating film of yttrium oxide or yttrium aluminum garnet(hereinafter, referred to also as “YAG”) having a thickness of 10 μm ormore, a film thickness variance of 10% or less and, preferably, asurface roughness Ra of 1 μm or less is formed on a surface of a membercontaining quartz glass, and also relates to a method for producing amember for a plasma etching apparatus in which a coating film of yttriumoxide or YAG is formed on a surface of a member for a plasma etchingapparatus containing quartz glass, aluminum, alumite or a combinationthereof by any one of a method of plasma-spraying yttrium oxide or YAG,a method of fusing yttrium oxide or YAG powder by an oxyhydrogen flameand, then, performing coating by using the thus-fused article, a methodof applying a solution in which yttrium, a yttrium compound or YAG isdissolved and, then, performing heat-fusing and a combination of thesemethods.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention is described in detail.

A member for a plasma etching apparatus according to the inventioncontains quartz glass, and has on a surface thereof a coating film ofyttrium oxide or YAG having a film thickness of 10 μm or more, a filmthickness variance of 10% or less and, preferably, further, a surfaceroughness Ra of 1 μm or less. When the film thickness of theabove-described coating film of yttrium oxide or YAG is less than 10 μm,a pinhole tends to be generated and thickness of a ridge portion becomesextremely small, to thereby generate a crack. Further, when the surfaceroughness Ra is over 1 μm, electric properties on a surface of thecoating film are partially changed, to thereby generate an abnormaletching. Further, when the film thickness variance is more than 10%,although the surface roughness Ra of the coating film is 1 μm or less, alarge undulation is generated and, then, due to this large undulation,electrical properties of the coating film are deteriorated, to therebyeasily generate a pinhole by plasma. Preferably, the ridge portion ofthe member is subjected to rounding machining so as to have a size of R0.5 mm or more and, then, yttrium oxide of YAG is applied as a coatingfilm. By this rounding machining, the thickness of the coating film isprevented from becoming small, to thereby suppress generation ofpinholes. As for the rounding machining in a case of a member containingquartz glass, a method of machining the ridge portion by an oxyhydrogenflame, a method of mechanically polishing the ridge portion by a grinderor the like or a method of blowing crystalline silicon dioxide powder,silicone carbide powder or the like on the ridge portion can be adopted.

A member in which a member is previously formed by using quartz glasscontaining yttrium oxide or YAG in the range of from 1 to 10% by weightand, then, on the thus-formed member, the coating film of yttrium oxideor YAG is formed. By performing such arrangement as described above,difference of coefficient of thermal expansion between the member andthe coating film of yttrium oxide or YAG becomes smaller, to therebydecrease film separation, enhance plasma resistance, suppress generationof the particle and expand a service life.

Next, an aspect of the method for producing the member for the plasmaetching apparatus according to the present invention is described.Namely, there is a production method in which a starting materialcontaining quartz glass, is machined to form a member for a plasmaetching apparatus and, then, on the thus-formed surface of the member, acoating film of yttrium oxide or YAG is formed by any one of (i) amethod of plasma-spraying yttrium oxide or YAG, (ii) a method of fusingyttrium oxide or YAG powder in an oxyhydrogen flame and, then,performing coating with the thus-fused article, (iii) a method ofapplying a solution in which yttrium, a yttrium compound or YAG isdissolved on a member, drying the thus-applied solution and, then,heat-fusing the thus-dried article by the oxyhydrogen flame(hereinafter, referred to also as “solution application method”), and acombination of these methods. After a coating film of yttrium oxide orYAG is formed by the solution application method among these methods,when yttrium oxide or YAG is plasma-sprayed on the thus-formed coatingfilm, a film thickness comes to be large and, further, a homogeneousyttrium oxide or YAG coating film is formed, which is preferred. It ispreferable that a film thickness of the coating film of yttrium oxide orYAG is 10 μm or more, a coating film variance is 10% or less and,preferably, further, a surface roughness Ra is 1 μm or less. As foryttrium compounds to be used by the solution application method, ahydroxide, a nitrate, a carbonate, a sulfate, an oxalate thereof and thelike are mentioned. As for solvents for use in dissolving the yttrium,yttrium compounds or YAG, pure water, an organic solvent is mentioned. Acoating solution is prepared by dissolving yttrium, the yttrium compoundor YAG. In the solution application method, in order to prevent thegeneration of the pinhole, the solution is preferably applied 3 times ormore.

A surface of the member is preferably subjected to a rougheningtreatment prior to coating with yttrium oxide or YAG. By such treatment,the coating film becomes difficult to be slipped and, then, filmseparation can be prevented. The term “frost treatment” as used hereinmeans to provide irregularity on a surface of quartz glass by a physicalmeasure or a chemical measure. As for such physical measures, there area so-called sandblast method in which crystalline silicon dioxidepowder, silicon carbide powder or the like is blown by compressed air, amethod in which crystalline silicon dioxide powder, silicon carbidepowder or the like is provided on a brush and, then, the surface thereofis polished by using the resultant brush while being wet with water andthe like. Further, as for such chemical measures, there are a chemicalsolution treatment method in which the member is dipped in a mixedreagent of hydrogen fluoride and ammonium fluoride and the like.Particularly, in the chemical measure, since a micro-crack is notgenerated on the surface and mechanical strength of quartz glass on thesurface is not deteriorated, the chemical measure is preferred. Thesurface roughness Ra to be formed by the frost treatment is preferablyin the range of from 0.1 to 10 μm. In a case in which the surfaceroughness Ra is beyond this range, adhesiveness between the coating filmof yttrium oxide or YAG and quartz glass is not sufficiently improved;accordingly, the case is not preferred.

Hereinafter, the present invention is specifically described withreference to embodiments but is not limited thereto.

COMPARATIVE EXAMPLE 1

A quartz glass chamber for a dry etching apparatus for a 12-inch Siwafer was prepared. A ridge portion of the chamber was subjected torounding machining so as to have a size of R 2 mm by blowing crystallinesilicon dioxide powder on an inner surface of the thus-prepared quartzglass chamber. Further, by blowing crystalline silicon dioxide powder(grain diameter: 100 to 300 μm) also on an entire inner surface of thechamber, the inner surface was allowed to be an irregular face having asurface roughness Ra of 2.5 μm and a Rmax of 20 μm. On the thus-formedinner surface of the quartz glass chamber, Y₂O₃ was plasma-sprayed, tothereby form a Y₂O₃ coating film having a thickness of 40 μm. A surfaceroughness Ra of the coating film was 0.2 μm and a film thicknessvariance thereof was 12%.

Inside the above-described quartz glass chamber, a gas mixture of CF₄+O₂was allowed to be in a plasmatic condition and, then, an oxide film ofthe 12-inch Si wafer was etched. Although this chamber was used for 5weeks, there was no incidence in which the Y₂O₃ coating film was etchedto expose the quartz glass and there was no generation of an abnormalparticle on a surface of the Si wafer.

COMPARATIVE EXAMPLE 2

A quartz glass chamber of 12 inch was prepared by using quartz glass ina same manner as in Reference Example 1. A ridge portion of this chamberwas subjected to rounding machining by being heated by an oxyhydrogenflame so as to have a size of R 1 mm. Further, the quartz glass chamberwas subjected to an etching treatment by using a chemical solution ofhydrofluoric acid and ammonium fluoride, to thereby form an irregularface having an Ra of 1.5 μm and a Rmax of 13 μm on an inner surfacethereof. On the thus-formed inner surface of the chamber, YAG wasplasma-sprayed, to thereby form a YAG coating film of 50 μm. A surfaceroughness Ra of the YAG coating film on this occasion was 0.5 μm and afilm thickness variance thereof was 8%.

Inside the above-described quartz glass chamber, a gas mixture of CF₄+O₂was allowed to be in a plasmatic condition and, then, an oxide film ofthe 12-inch wafer was etched. Although this chamber was used for 5weeks, there was no incidence in which the YAG coating film was etchedto expose the quartz glass and there was no generation of an abnormalparticle on a surface of the Si wafer.

COMPARATIVE EXAMPLE 3

An aluminum cover for a dry etching apparatus for a 12-inch Si wafer wasprepared. A surface of the aluminum cover was subjected to an alumitetreatment. A ridge portion of the aluminum cover was subjected torounding machining so as to have a size of R 1 mm and, then, an outersurface thereof was plasma-sprayed with Y₂O₃, to thereby form a Y₂O₃coating film of 200 μm. A surface roughness Ra of the Y₂O₃ coating filmon this occasion was 0.1 μm and a film thickness variance thereof was15%.

Inside the etching apparatus provided with the aluminum cover, a gasmixture of CF₄+O₂ was allowed to be in a plasmatic condition and, then,an oxide film of the 12-inch wafer was etched. Although this cover wasused for 5 weeks, there was no incidence in which the Y₂O₃ coating filmwas etched to expose aluminum and there was no generation of an abnormalparticle on a surface of the Si wafer.

COMPARATIVE EXAMPLE 4

Quartz powder was blended with 5% by weight of Y₂O₃ powder and, then,sufficiently homogeneously mixed by a ball mill. The resultant startingmaterial was fused in an oxyhydrogen flame, to thereby prepare an ingotof quartz glass. From the ingot which is a base material, a quartz glasschamber for a dry etching apparatus of 12-inch Si wafer was prepared.Crystalline silicon dioxide powder (100 to 300 μm) was blown on an innersurface of this chamber, to thereby form an irregular face having asurface roughness Ra of 2.5 μm and an Rmax of 20 μm. Then, Y₂O₃ wasplasma-sprayed on the thus-formed inner face of the chamber, to therebyobtain a Y₂O₃ coating film having a thickness of 150 μm. A surfaceroughness Ra of the coating film was 0.5 μm and a film thicknessvariance thereof was 10%.

Inside the above-described quartz glass chamber, a gas mixture of CF₄+O₂was allowed to be in a plasmatic condition and, then, an oxide film ofthe 12-inch Si wafer was etched. Although this chamber was used for 12weeks, there was no incidence in which the Y₂O₃ coating film was etchedto expose the quartz glass and there was no generation of an abnormalparticle on a surface of the Si wafer.

COMPARATIVE EXAMPLE 5

A quartz glass chamber for a dry etching apparatus for a 12-inch Siwafer was prepared. A ridge portion of this chamber was subjected torounding machining by being heated by an oxyhydrogen flame so as to havea size of R 1 mm. Further, an inside of the chamber was subjected to anetching treatment by using a chemical solution of hydrofluoric acid andammonium fluoride, to thereby form an irregular face having a surfaceroughness Ra of 2.5 μm and a Rmax of 20 μm. On the thus-formed innersurface of the chamber, an yttrium nitrate solution was applied 4 times,dried and, then, heat-fused by the oxyhydrogen flame, to thereby obtaina Y₂O₃ coating film of 50 μm. A surface roughness Ra of the coating filmwas 0.5 μm and a film thickness variance thereof was 8%.

Inside the above-described quartz glass chamber, a gas mixture of CF₄+O₂was allowed to be in a plasmatic condition and, then, an oxide film ofthe 12-inch Si wafer was etched. Although this chamber was used for 12weeks, there was no incidence in which the Y₂O₃ coating film was etchedto expose the quartz glass and there was no generation of an abnormalparticle on a surface of the Si wafer.

COMPARATIVE EXAMPLE 1

A quartz glass chamber for a dry etching apparatus for a 12-inch Siwafer was prepared. Inside this quartz glass chamber, a gas mixture ofCF₄+O₂ was allowed to be in a plasmatic condition and, then, an oxidefilm of the 12-inch Si wafer was etched. When this chamber was used for2 weeks, an abnormal particle was generated on a surface of the Si waferand, accordingly, the chamber was stopped using for more than one week.

COMPARATIVE EXAMPLE 2

An aluminum cover for a dry etching apparatus for a 12-inch Si wafer wasprepared. A surface thereof was subjected to an alumite treatment. Apolyimide tape of 125 μm was attached to an outer surface of thethus-treated aluminum cover. In an etching apparatus provided with thisaluminum cover, a gas mixture of CF₄+O₂ was allowed to be in a plasmaticcondition and, then, an oxide film of an 8-inch wafer was etched. Whenthis cover was used for 2 weeks, a gap of the polyimide tape wasabnormally etched to expose aluminum and, then, irregularity wasgenerated on the surface thereof, to thereby partially accelerateetching and generate a pinhole on the polyimide tape. 2 weeks later, thepolyimide tape was removed and a new polyimide tape was attached again.When the resultant aluminum cover was set on the apparatus, an abnormalcontamination was noticed on the wafer and, then, the apparatus wasstopped using.

COMPARATIVE EXAMPLE 3

An aluminum cover for a dry etching apparatus for a 12-inch Si wafer wasprepared. A surface thereof was subjected to an alumite treatment. In anetching apparatus provided with this aluminum cover, a gas mixture ofCF₄+O₂ was allowed to be in a plasmatic condition and, then, an oxidefilm of the 12-inch Si wafer was etched. When this cover was used for 2weeks, the alumite was removed 1 week after the start of the usage andgeneration of a particle was noticed on a surface of the wafer and,then, the apparatus was stopped using.

INDUSTRIAL APPLICABILITY

The member for the plasma etching apparatus according to the presentinvention has a high plasma resistance and, further, is not subjected toan abnormal etching on the basis of a partial change of electricproperties and, accordingly, can be used for a long period of time.Particularly, even when the member is large enough to handle a 12-inchSi, the above-described properties are maintained and, then, it can beused for long period of time.

1. A member for a plasma etching apparatus, consisting of a coating filmof yttrium oxide having a film thickness of 10 μm or more and athickness variance of 15% or less formed on a frost-treated surface ofthe member, said member comprising quartz glass and 1 to 10% by weightof yttrium oxide.
 2. A member for a plasma etching apparatus, consistingof a coating film of YAG having a film thickness of 10 μm or more and athickness variance of 15% or less formed on a frost-treated surface ofthe member, said member comprising quartz glass and 1 to 10% by weightof YAG.
 3. The member for the plasma etching apparatus according toeither of claims 1 or 2, wherein the surface roughness Ra of the coatingfilm is 1 μm or less.